Feature Articles

  1. Successful High-Precision QoS Measurement In Widely Deployed 10-Gbit/s Networks Based On General-Purpose Personal Computers
    8/31/2010
    NTT Laboratories has developed a 10-Gbit/s PCI (peripheral component interconnect) network interface card (NIC) with network measurement extensions (measurement NIC). It works both as a normal NIC for a 10-Gbit/s network and as a measurement NIC. Its extensions enable precise measurements of the network status and quality of service (QoS). It will let us develop a reliable network measurement system based on inexpensive general-purpose personal computers (PCs). This article describes techniques for building 10-Gbit/s wire-rate precise network measurement systems that can measure the quality of service (QoS) of high-speed networks precisely and quickly, even with non-sampling measurements.
  2. The Design Of E-Band MMIC Amplifiers
    8/4/2010
    The worldwide availability of a large amount of spectrum at 71-76GHz and 81-86 GHz (commonly known as "E-band") for high data-rate wireless links has led to substantial interest. The design of electronic equipment at such high frequencies is challenging. Parasitic effects that were negligible at microwave frequencies become problematic and the availability of suitable active components is very restricted. The development of custom GaAs MMICs offers a route to realising low-cost, reproducible E-band components. This article addresses the design and implementation of E-band MMIC amplifiers. It considers process selection, design challenges and practical approaches and presents the measured and modelled performance of a single-stage E-band gain block.
  3. What's The Best Wireless Transport Option For Uncompressed HDTV Video?
    8/3/2010
    Once the exclusive realm of scientific research and military use, wireless systems operating in the upper millimeter wave (MMW) regions are now providing cost-effective solutions for high-capacity commercial data transport needs. The unique attributes of MMW signal propagation, combined with the scarcity of RF spectrum at lower frequencies, assures that the proliferation of MMW systems and their effect on daily life will continue. This article examines the unique attributes of signal propagation in the MMW region. The goal of this analysis is to provide the reader with a general, working knowledge to make informed decisions when considering MMW solutions.
  4. What’s The Value Of ZigBee?
    7/26/2010
    Today NXP announced that it is acquiring Jennic, the UK based RF design company that specialises in ZigBee chips and stacks. That in itself is not surprising. The market for ZigBee silicon has been consolidating for some time, with the previous acquisitions of One RF, Chipcon and module vendor Meshnetics. It's something that I predicted would happen last year. It's good news for the design team at Jennic, as NXP should provide them with the scale to grow and a sales infrastructure and industry stature that increases their customer base.
  5. Budgeting Harmonics For ZigBee Front-End Modules
    7/13/2010
    The growth of low-power, cost-effective wireless radio systems is driving more applications to use the ZigBee communication standard. Some of these applications require a signal to propagate over a short range. When installed in a large building or operating outdoors over a wide area, such a system may benefit from transmitting more power. This article details how to specify harmonics for a ZigBee Front-End Module (FEM). Requirements from the different regulatory standards are reviewed and analyzed using the simulation harmonic content of Offset Quadrature Phase-Shift Keying (OQPSK) spread spectrum modulation. The effects of the measurement bandwidth and detector on the harmonics level of both sine and ZigBee waveforms are also evaluated.
  6. Managing TDD-FDD Interference Between Co-Sited Base Stations Deployed In Adjacent Frequency Blocks
    7/13/2010
    In many urban and semi-rural areas new base station sites can be difficult to obtain leading to new operators being required to share sites with existing operators. In such circumstances it is generally necessary to minimize inter-network interference especially between TDD and FDD systems operating in adjacent spectrum blocks. This article reports an analysis and measurement campaign which concludes that inter-network interference between co-sited base stations can be readily reduced to a manageable level with minimal impact on system capacity through careful antenna siting during deployment. Co-sited base station operation is entirely possible even between TDD and FDD (or TDD)system adjacencies.
  7. The Case For GPS Simulation
    7/1/2010
    As demand for precision GPS receivers continues to grow through a number of industries and applications, increased attention to focused GPS receiver test can land you ahead of the competition. With a GPS simulator, you have full control over signal power levels, Doppler shifts, ephemeris errors, multi-path fading, ionospheric effects, and many other impairments found in real-world GPS signals. By simulating a GPS signal, you can introduce each of these impairments individually or in scenario-specific combinations for the targeted troubleshooting needed to truly improve your design.
  8. Time-Saving Technologies To Simulate And Tune Conformal Antennas For Modern Mobile Devices
    6/24/2010
    The bottlenecks for simulation tools used for antenna design are typically in two areas: project setup and simulation speed. By reducing the time spent in these two areas, RF engineers have more time to design their antennas. Modern full wave simulation tools should effectively address this situation. XF7 from Remcom is designed to reduce these bottlenecks in several ways, including parameterization, scripting, advanced meshing techniques, and GPU implementation of the computational algorithm.
  9. Measuring LTE Modulation Quality Over-The-Air With A Handheld Instrument
    6/10/2010
    This article presents a simpler and faster method of measuring modulation quality—making the measurement over-the-air with a handheld instrument. This method is based on the fact that control channels do not use spatial multiplexing or beamforming because they have to operate over the entire cell, including at the cell edges. Over-the-air measurements of LTE modulation quality are not intended to replace direct-connect measurements because direct-connect measurements are more accurate and comprehensive. However, over-the-air measurements are much faster and more convenient so they provide a valuable tool to help meet the challenge of delivering seamless LTE service.
  10. A Comparison Of Measurement Uncertainty In Vector Network Analyzers And Time Domain Reflectometers
    5/28/2010
    Measurement uncertainty has a direct impact on the reliability of test instruments. To determine if there is a quantifiable difference in measurement uncertainty between the TDR and VNA, W. L. Gore & Associates performed a series of experiments, initially testing six cable assemblies in controlled conditions on each instrument. The instruments' measurement uncertain under best-case scenario was evaulated using the highest-performing assembly. To ensure TDR/VNA test parity, the VNA's performance was evaluated using a s11 one-port reflection method as well as the more traditional s21 two-port transmission method.

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